Filtering device with enhanced bleeding assembly and diesel fuel supply line comprising same

ABSTRACT

The device ( 6 ) includes a sealed casing ( 10 ) provided, in its lower part, with a bowl ( 22 ) for collection of a residual liquid, and an assembly ( 30 ) for purging the residual liquid which comprises means for evacuation of the liquid collected in the bowl and means for connecting the casing to the open air.  
     The means for evacuation of the liquid include an orifice ( 36 ) formed in the wall of the casing substantially at the level of the bottom of the bowl ( 22 ). The means for connection to the open air include an orifice ( 34 ) formed in the wall of the casing ( 10 ) substantially opposite the orifice ( 36 ) for evacuation of the liquid. A single obturator ( 40 ) is displaceable between a sealing position in which, on the one hand, its upper part forms a tight plug ( 42 ) for the orifice for entry of air ( 34 ) and, on the other, its lower part forms a tight plug ( 48 ) for the orifice for evacuation of the liquid ( 36 ), and a position for purging the liquid in which, on the one hand, its upper part is disengaged from the orifice for entry of air to allow connection of the casing to the open air and, on the other, its lower part is disengaged from the orifice for evacuation of the liquid to allow gravity purging of the casing.

The present invention relates to a filtration device with an improvedpurge assembly, of the type defined in the preamble of claim 1.

It is preferably applied to the field of filtration of gas-oil, inparticular for low pressure gas-oil supply lines of diesel engines, forexample of vehicles or machines.

Such devices are intended to separate from a liquid or gaseous mixture aliquid impurity which progressively accumulates in a collection bowl.

In the case of gas-oil, these devices permit separation from the gas-oilof the water which the gas-oil contains in emulsion. This water isseparated from the gas-oil by suitable filtration means, such as a meshand/or a paper filter, and accumulates by gravity in a lower collectionbowl.

For proper operation of the device, it is periodically necessary topurge the residual liquid. For this purpose, a liquid evacuation orificeis formed in the wall of the collection bowl and generally provided witha plug screwed on in sealed manner; similarly, an obturatable orificefor connection to the open air is provided in the wall of the casing,generally in its upper part. The purge can only be performed when bothorifices are open, for, as is well known, the liquid removed from insidea sealed container under the influence of gravity has to be replaced bya fluid, for example the outside air.

In certain devices, the orifice for connection to the open air issuitable to be closed by a plug screwed on in sealed manner, the gravitypurge then being caused by unscrewing the two plugs.

For other devices, such as that described in GB 157 669, the orifice forconnection to the air is formed by an orifice used for taking off thefiltered gas-oil downstream of the casing, this orifice, outwith purgeperiods, being connected in sealed manner to for example an outlet pipefor the filtered gas-oil. In addition, the device described in GB 157669 includes a valve for closing an orifice for supply of gas-oil to befiltered, which can be operated by means of the screwed plug for closureof the orifice for evacuation of the residual liquid, so that opening ofone of the orifices for evacuation and supply simultaneously causesclosure of the other of these orifices, and vice versa.

In all cases, these devices therefore have the disadvantage of a doublemanipulation to perform the purge. For a device for filtration ofgas-oil integrated in the gas-oil feed line of a diesel engine, thisdisadvantage is the more marked as the size of the zone in which thisline is installed often makes access to the filter casing difficult.

Moreover, to ensure good tightness of the casing outwith the purgeoperation, it is necessary to provide each closure organ manipulatedwith sealing packing resistant to repeated stresses. For example, eachscrewed plug must be provided with a flat washer, which always runs therisk of being forgotten, improperly positioned, or prematurely worn dueto its exposure to the external environment.

The aim of the present invention is to propose a device of theabove-mentioned type which permits an easy and quick purge operation andwhich minimises the risks of subsequent malfunctioning of the filtrationdevice.

To this end, the invention has as its object a device of theabove-mentioned type which has the characteristics of the characterisingpart of claim 1.

Other characteristics of this device, taken in isolation or in alltechnically possible combinations, are stated in dependent claims 2 to26.

The invention also has as its object a gas-oil supply line, inparticular for a diesel engine, having the characteristics of claim 27.

The invention will be better understood on reading the followingdescription, given solely by way of example and with reference to theattached drawings in which:

FIG. 1 is a diagrammatic view of a gas-oil supply line in accordancewith the invention;

FIG. 2 is a perspective view of a gas-oil filtration device inaccordance with the invention;

FIGS. 3 and 4 are partial views in longitudinal section of the purgeassembly of the device of FIG. 2, this assembly being in the sealedposition in FIG. 3 and in the purge position in FIG. 4;

FIG. 5 is a perspective view of an alternative embodiment of the gas-oilfiltration device in accordance with the invention;

FIG. 6 is a frontal view of the heating unit of the device of FIG. 5;

FIG. 7 is a perspective view, at the same angle as that of FIG. 2, ofthe filtration unit of the device of FIG. 5;

FIG. 8 is a view similar to that of FIG. 6 of an alternative embodimentof the heating unit in accordance with the invention;

FIG. 9 is a view in section through the plane IX-IX indicated in FIG. 8;and

FIG. 10 is a view in the direction of the arrow X indicated in 15 FIG.8.

FIG. 1 shows a gas-oil supply line 1 of a diesel engine 2. The line 1 isa low pressure line, i.e. the gas-oil is displaced in this line, asindicated by the arrows, due to a depression at is downstream endrelative to its upstream end. The line 1 includes, from upstream todownstream, a gas-oil tank 4, a device 6 for filtration of the gas-oil,and a gas-oil pump 8.

With the exception of the device 6, which will be described in detailhereinafter, the tank 4 and the pump 10 are elements known in themselvesand will not be firstly described in detail.

The device 6 includes, for the embodiment shown in FIGS. 1 to 4, a unit7 for filtration of the gas-oil in order to remove water in emulsionfrom it. As shown in FIGS. 1 and 2, the filtration unit 7 includes acasing 10, for example made of plastics material and of substantiallyparallelepipedal general shape. Internally, the casing 10 defines afiltration chamber in which in known manner are arranged filtrationmeans 12 suitable to retain the water in emulsion in the gas-oil. Thesefiltration means, diagrammatically outlined in FIG. 1, are for exampleformed of a mesh of determined pore size and/or of filter paper whichretain and evacuate to their lower part the water with which the gas-oilpassing through them is charged. To this end, the casing 10 of the unit7 includes, on the one hand, an orifice 14 for intake of the gas-oilcharged with water, connected to the tank 4, via a connection 16, and,on the other, a pipe 18 for outlet of the gas-oil substantially freefrom water, connected to the pump 8, via a connection 20.

The unit 7 also includes a bowl 22 for collection of the water separatedfrom the gas-oil by the means 12. This bowl is arranged in the lowerpart of the casing 10 and has a large water storage capacity which mustbe periodically purged.

To this end, the device 6 includes a purge assembly 30 able to allow thewater contained in the bowl 22 to freely follow an outflow pipe 32,rigidly attached to the bottom part of the casing 10.

More precisely, and as shown in detail in FIGS. 3 and 4, the purgeassembly 30 includes a first orifice 34 for connection to the open airformed in the upper wall 35 of the casing 10. This orifice is ofgenerally cylindrical form with a substantially vertical axis. It isdefined by a threaded upper part 34A, a substantially smooth lower part34B and an intermediate shoulder 34C, the diameter of the lower partbeing slightly smaller than that of the upper part.

The purge assembly 30 includes a second orifice 36 formed in the lowerwall 37 of the casing 10, substantially on the perpendicular to theupstream end of the outflow pipe 32. This orifice 36 is positionedsubstantially opposite the first orifice 34, or even, as shown in thefigures, coaxially. The orifice 36 is defined [by] a substantiallycylindrical and smooth lower part 36A, of smaller diameter than that ofthe lower part 34B of the first orifice 34, and an upper part 36Bsubstantially in the form of a truncated cone, the diameter decreasingdownwardly, in which is formed at least one notch 36C to allowconnection of the orifice 34 to the bowl 26 at the lowest possiblelevel.

The purge assembly 30 also includes a rod 40 forming an obturator of theorifices 34 and 36. The rod 40 is displaceable with a substantiallyvertical movement of translation between a low position in which itseals the casing 10, as shown in FIG. 3, and a high position it allowsgravity purging of the bowl 22, as shown in FIG. 4.

The rod 40 includes an upper part 42, partially threaded so as toco-operate with the threaded part 34A of the orifice 34. It includes,also in its upper part, an annular groove provided with an O-ring 44suitable to be pressed against the cylindrical surface 34B of theorifice 34 when the rod 40 is in the sealing position, and to bepositioned without being pressed at the level of the shoulder 34C of theorifice 34 when the rod is in the purge position.

The rod 40 also includes at its upper end a head 46 facilitating itshandling during screwing-unscrewing manoeuvres. This head 46 isadvantageously so arranged relative to the casing as to be able to beeasily manoeuvred, in particular taking into account the size of thezone in which the line 1 of FIG. 1 is arranged.

The rod 40 includes a lower end part 48 of generally cylindrical formand terminated by a bevel 49, substantially in the form of a truncatedcone, the lateral surfaces of which are for example substantiallycomplementary to the surface of the part 36B substantially in the formof a truncated cone of the orifice 36 of the casing 10. The part 48 ofthe rod also includes an annular groove provided with an O-ring 50 ofsmaller diameter than the O-ring 44. This O-ring 50 is suitable to bepressed against the cylindrical surface 36A of the orifice 36 when therod is in the purge position. The lower part 48 of the rod 40 thus formsa tight plug for the orifice 36 when the rod is in the sealing positionand allows evacuation of the water into the pipe 32 through the orifice36, in the direction of the solid arrow shown in FIG. 4, when it is inthe purge position.

The rod 40 also includes a substantially flat lower end face 52 suitableto bear firmly on a wall part 54 rigidly attached to the casing 10 andarranged at the upstream end of the pipe 32.

In addition, the rod 40 includes a standard part 56 in the form of asolid cross-piece of smaller cross-section than that of the remainder ofthe rod. This structure is sufficiently transversally flexible to takeup possible play due to faulty alignment of the respective axes of theorifices 34 and 36. Such take-up can also be envisaged by means of aflexible material forming the standard part 56.

The operation of the filtration device in accordance with the inventionis as follows.

In service, that is to say when the device 6, by means of its filtrationunit 7, is filtering water from the gas-oil circulating in the lowpressure line 1 of FIG. 1, the water is collected in the bowl 22. Therod 40 is occupying the position of FIG. 3 and provides proper sealingof the casing at the level of the orifices 34 and 36 by means of thesealing rings 44 and 50, pressed against 10 their respective sealingsurfaces 34B and 36A.

At the purge operation of the device 6, the rod 40 is unscrewed by asufficient number of turns, for example three, by means of its head 46,so that, overall, it is displaced with a movement of upward translationto attain its purge position of FIG. 4. In this position, the upperO-ring 44 is no longer pressed against a sealing surface with the resultthat the air can freely enter the inside of the casing 10 through theorifice 34. Similarly, the lower part 48 of the rod frees the lowerorifice 36 through which the water is freely evacuated into the pipe 32,under the influence of gravity.

Once the purge is complete, the rod 40 is screwed back into its sealingposition. Its lower part 48 is then guided in translation by the part36B in the form of a truncated cone of the orifice 36, while its upperpart 42 positions the O-ring 44 in tight contact with the part 34B ofthe orifice 34. Continuing the screwing back of the rod 40, the lowerO-ring is then positioned in tight contact against the surface 36A ofthe orifice 36 and the lower end section 52 of the rod abuts firmlyagainst the wall part 54.

Thus, the filtration device in accordance with the invention allows thegravity purge of the filter casing to be performed easily and quickly.In fact the purge operation only requires the manipulation a singleplug, instead of two for the relevant devices of the prior art.

In addition, the purge assembly of the device in accordance with theinvention does not require sealing pieces attached at the end of thepurge operation, such as a washer, as the O-rings 44 and 50 arepermanently arranged on the obturator 40.

Moreover, a same rod 40 can be used with a plurality of successive cases10, in particular when these are changed for reasons of saturation orwear of the filtration means 12. In fact, by completely unscrewing thethreaded section 42 from the associated tapped part 34A of the orifice34, the complete rod 40 can be withdrawn from the casing, the diametersof its lower part and of the O-ring 50 being smaller than that of thecylindrical part 34B of the orifice 34. The rod 40 is then introducedinto a new filter casing, its lower part being guided during itsintroduction by co-operation of its lower end bevel 49 with the part 36Bin the form of a truncated cone of the orifice 36.

In addition, it is unnecessary to manufacture the casing 10 withstringent geometrical tolerances, a certain straying of the geometricalcharacteristics of the casing being absorbed by the purge assembly 30.On the one hand, possible transversal differences linked to the orifices34 and 36 formed in the casing, for example due to faulty alignment ofthe axes of these orifices, are taken up both by the flexible standardpart 56 of the rod 40 and by the firm contact of the end section 52 onthe wall part of the casing 54. On the other hand, possible verticaldifferences between the upper 35 and lower 37 walls of the casing arerendered acceptable by sufficient over-dimensioning of the length ofeach of the sealing surfaces 34B and 36A.

Various arrangements of the purge assembly can be envisaged withoutdeparting from the scope of the invention. Thus, by way of amodification, the displacement of the rod 40 from its sealing positionto its purge position can be effected by other types of connection thanthat of a threaded connection. Similarly, the manoeuvring head 46 of therod 40 is not necessarily arranged at its upper end, but can be so atits lower end.

FIGS. 5 to 10 show a device 106 for filtration of gas-oil in accordancewith the invention, a modification of the one shown in FIGS. 1 to 4.This device 106 is essentially distinguished from that of FIGS. 1 to 4by the fact that it includes, in addition to a filtration unit 114having a function substantially similar to the unit 7 of FIGS. 1 to 4, aunit 110 for electrical heating of the gas-oil to be filtered, tintedgrey relative to the heating unit 114 of FIG. 5, and suitable tofluidise the gas-oil when it is used cold.

The filtration unit 114 is provided with a purge assembly 30 inaccordance with the invention, similar to that of FIGS. 2 to 4. Thispurge assembly is indicated in FIGS. 5 to 7 by the same references asthose of FIGS. 2 to 4, and will not therefore be described in detailagain with reference to these figures.

As indicated by the arrows of FIG. 5, the heating unit 110 is arrangedupstream, in the direction of displacement of the gas-oil in the device,of the filtration unit 114, so that the device 106 is suitable to bearranged in a gas-oil supply line of a diesel engine, for exampledownstream of a tank and upstream of a gas-oil pump supplying thisengine.

As shown in more detail in FIG. 6, the heating unit 110 includes acasing 120 of substantially parallelepipedal general shape and defininginternally a chamber, not shown in the figures, for heating the gas-oil.For this purpose, the unit 110 includes internally one of moreelectrical heating elements.

These elements, themselves known, are arranged in the heating chamberand electrically connected to an electrical connector 122. Thisconnecter is arranged on the casing 120 and intended to receive anelectrical power supply cable, for example connected to a battery ofaccumulators.

The unit 110 externally includes a coupling sleeve 124 for input of thegas-oil to be heated into the heating chamber and a coupling sleeve 126for outlet of the heated gas-oil, on which are arranged two O-ring seals127.

These coupling sleeves extend in the longitudinal direction of thecasing 120, the latter being made, for example, of rigid plasticsmaterial and the intake 124 and outlet 126 sleeves being moulded in onepiece with the casing 120.

In addition, the casing 120 has notable external characteristics, ofwhich account will be given hereinafter. Firstly, it includes asubstantially flat longitudinal face; in the example shown, this is theface not visible in FIG. 6, opposite to the longitudinal face on whichthe intake sleeve 124 is arranged. In addition, its upper face includes,in its part most distant from the outlet sleeve 126, a protuberance 128.This protuberance includes, on the side of the outlet sleeve 126, agentle slope 128A and, on the opposite side, a slope with notches 128B.In addition, the lower face of the casing 120 includes a longitudinalrail 130 of continuously decreasing thickness as it approaches the sideof the outlet sleeve 126.

FIG. 7 shows in detail the filtration unit 114. This includes a casing140 of substantially parallelepipedal general shape defining internallya chamber, not shown in the figures, for filtration the gas-oil. Forthis purpose, the unit 114 includes internally filtration means, such aspaper, a Nylon mesh, etc. . . . which are known in themselves. Thesemeans permit both retention of the water which the gas-oil contains inemulsion, evacuating it into a collection bowl 141 similar to the bowl22 described with reference to FIGS. 1 to 4, and retention of solidimpurities possibly present in the gas-oil. Once these filtration meansare saturated, the whole of the filtration unit 114 should be exchangedwith a new unit.

In addition to the purge assembly 30 and corresponding arrangements ofits casing 140, the unit 114 includes externally a sleeve 142 for outletof the purified gas-oil. In addition, a tubular orifice 144 is formed inthe wall of the casing 140 so as to receive the outlet sleeve 126 of theheating unit 110.

The casing 140 of the filtration unit 114 is formed of a plasticsmaterial substantially similar to that of the casing 120 of the heatingunit 110. By complementarity of shape, the casing 140 is able to supportand hold in place, detachably, the casing 120. For this purpose, thecasing 140 presents externally a substantially flat surface 146 ofdimensions substantially complementary to those of the above-mentionedflat longitudinal face of the casing 120. In addition, the casing 140includes a tab 148, providing a slot 149 for reception of theprotuberance 128 on the casing 120. The tab 148 is connected to thecasing by two arms 148A, 148B, of which at least the arm 148A issectile, for example by means of suitable dimensioning. Moreover, thecasing 140 includes a slideway 150 for sliding of the longitudinal rail130 of the casing 120. In the example shown, the slideway includes twoparts 150A and 150B, the part 150A substantially opposite the arm 148Abeing of stronger structure than the second part 150B.

Assembly of the casing 120 of the heating unit 110 with the casing 140of the filtration unit 114 is effected in the following manner:

The heating unit 110 is firstly so positioned relative to the filtrationunit 114 that the surface 146 of the casing 140 is substantially flushwith the above-mentioned flat longitudinal face of the casing 120. Then,by a movement of translation of the heating unit 110 relative to thefiltration unit 114, the longitudinal rail 130 of the casing 120, guidedby the slideway 150 of the casing 140, causes the outlet sleeve 126 ofthe casing 120 to enter the tubular orifice 144 of the casing 140. Thismovement of translation is continued until the protuberance 128, whichhas previously lifted the tab 148 both by means of its gentle slope 128Aand under the influence of raising of the casing 120 relative to thecasing 140 caused by the increasing thickness of the rail 130, is housedinside the slot 149.

The rear arm 148A, relative to the direction of the preceding movementof translation, of the tab 148 is thus engaged with a notch of thenotched slope 128B of the protuberance 128, then preventing the unit 10from disengaging from the unit 114. The protuberance 128 thus forms awedge for retaining the heating unit 110 in translation.

The heating 110 and filtration 114 units thus co-operate bycomplementarity of shape of their respective casings 120 and 140, sothat the sleeve 126 and the orifice 144 form direct and sealed means forconnecting the heating and filtration chambers.

Once the filtration device 106 is assembled as described above, itsoperation is as follows.

When the gas-oil is drawn into the low pressure line in which the device106 is arranged, the gas-oil enters the heating unit 110 where it is, ifnecessary, heated by the above-mentioned electric heating element orelements.

The gas-oil leaves the heating chamber of the unit 110 following theconnecting sleeve 126 between the units 110 and 114, and thus arrivesdirectly in the filtration chamber of the unit 114. It leaves it againthrough the outlet sleeve 142 and follows the evacuation pipe 116, forexample to a pump and a diesel engine.

The filtration device 106 is thus easy to install since, once the units110 and 114 are fixed one to the other, it is connected to the line likea standard single filtration element. Fixing of the heating unit to thefiltration unit is, for its part, accomplished by a single movement oftranslation of the one relative to the other. The O-rings 127 providegood tightness of the connection between the two units, even in thepresence of vibrations and/or slight axial misalignment between thesleeve 126 and the reception orifice 144.

To the extent that the sleeve 126 and the orifice 144 connect theheating and filtration chambers directly, the heated gas-oil sufferssubstantially no heat loss during its transfer from the heating chamberto the filtration chamber, moreover increasing the filtering performanceof the unit 114.

When it is necessary to purge the water retained in the collection bowl141, the operation of the purge assembly 30 is similar to that describedabove with reference to FIGS. 2 to 4.

In addition, when the filtration unit is saturated and ready to bediscarded to be replaced by a new filtration unit, it is only necessaryto cut the arm 148A of the tab 148. Breakage of the tab at the level ofits sectile part 148A releases the wedge 128 and allows the heating unit110 to be disengaged by a movement of translation in the oppositedirection to that required to fix the heating unit onto the filtrationone. The heating unit 110 is provided to have a longer life than that ofthe filtration unit 114, so it can be reused with several successivefiltration units. These maintenance operations also have the advantageof being clean, since none of the casings of the assemblies has to beopened. In addition, a filtration unit with a broken tab bears anobvious visual mark that it has already been used and can no longer holda heating unit in place.

FIGS. 8 to 10 show a modified embodiment of the unit 110 for heatinggas-oil of the filtration device 106 in accordance with the invention.The unit 110 of FIGS. 8 to 10 is only distinguished from that of FIGS. 5and 6 by the following.

In addition to the above-mentioned flat longitudinal face, visible inFIG. 10 and referenced 120A, the casing 120 of this heating unit 110includes a lower longitudinal rail 160 suitable to slide, in the samemanner as the rail 130 of FIGS. 5 and 6, in the slideway 150 of thecasing 140 of the filtration unit 114. Differently from theabove-mentioned rail 130, the rail 160 is of substantially constantthickness and includes a protuberance 162 formed on the part of the railmost distant from the sleeve 126. This protuberance is advantageouslymade in one piece with the rest of the rail 160. The face 162A, directedoppositely to the face 120A, of the protuberance 162 forms an angle,marked α, relative to the longitudinal direction of the rail 160, asshown in FIG. 9. This angle ox is for example of the order of a fewdegrees.

In addition, the protuberance 128 of this modified embodiment of theheating unit includes one single notch 128B. The face 128C of theprotuberance, intended to be turned towards the filtration unit 114,forms an angle of less than 90° with the substantially flat upper faceof the protuberance 128. This angle is marked P in FIG. 10 and isadvantageously 30°.

Assembly of the casing 120 of the heating unit 110, which has just beendescribed, on the casing 140 of the filtration unit 114 is performedsubstantially as described with regard to FIGS. 5 to 7.

On the movement of translation of the heating unit 110 relative to thefiltration unit 114, the lower rail 160 of the casing 120 is guided bythe slideway 150 of the casing 140. Progressively as the protuberance162, thus forming a ramp, is introduced into the strengthened part 150Aof the slideway 150, this protuberance 162 causes the casing 120 to beoffset transversally towards the casing 140.

Substantially concomitantly, the gentle slope 128A of the protuberance128 lifts the tab 148 until the protuberance 128 is housed inside theslot 148 defining the edge of the slot 149 comes into abutment againstthe inclined face 128C of the protuberance 128, then forming a ramp ableto transversally offset the casing 120, moving it away from the casing140.

The transversal position of the casing 120 is fixed by combination ofthe above-mentioned movements of transversal shift both of the lowerpart of the casing 120 of the casing 140 and of the upper part of thecasing 120 in the opposite direction.

Once the heating 110 and filtration 114 units are assembled, the casing120 is on the one hand retained in translation relative to the casing140, as for the embodiment of FIGS. 5 to 7, and on the other retainedtransversally to the direction of translation relative to the casing140.

The filtration device described with reference to FIGS. 8 to 10 has theadvantage of being more robust, its fixing means having bettermechanical resistance to vibration.

Various alternative embodiments of this modified embodiment of thefiltration device in accordance with the invention can be envisaged tothe 10 extent that, although using totally distinct casings, i.e. nothaving a common wall, but of substantially complementary shapes, theheating unit and the filtration unit are connected directly and in tightmanner to each other, for example by a short sleeve rigidly attached toone of the two units and essentially housed in the internal chamber ofthe other of these assemblies.

Also, various forms of casings are possible, in order to functionallyobtain an integrated filtration device, the respective casings of theheating and filtration assemblies of which co-operate by complementarityof shape, as described with reference to FIGS. 5 to 10.

Similarly, the means for fixing the heating unit onto the filtrationunit are transposable, without departing from the scope of theinvention, into means for fixing the filtration unit onto the heatingunit. For example, the slide rail can be arranged on the casing of thefiltration unit and the associated slideway is then arranged on thecasing of the heating unit.

1. Filtration device with improved purge assembly, of the type includinga filtration unit (7; 114) which comprises a sealed casing (10; 140)internally defining a filtration chamber provided with filtration means(12) and, in its lower part, a bowl (22; 141) for collection of aresidual liquid from the filtration means, and an assembly (30) forpurging the residual liquid which comprises means for evacuation of theliquid collected in the bowl and means for connection of the casing tothe open air, characterised by the fact that the means for evacuation ofthe liquid include an orifice (36) formed in the wall of the casingsubstantially at the level of the bottom of the bowl (22; 141) forcollection of the liquid, the means for connection to the open airincluding an orifice (34) formed in the wall of the casing (10; 140)substantially opposite the orifice for evacuation of the liquid (36),and the means for connection to the open air and the means forevacuation of the liquid include a single obturator (40) displaceablebetween a sealing position (FIG. 3) in which, on the one hand, its upperpart forms a tight plug (42) for the orifice for connection to the openair (34) and, on the other hand, its lower part forms a tight plug (48)for the orifice for evacuation of the liquid (36), and a gravity purgeposition (FIG. 4), in which, on the one hand, its upper part isdisengaged from the orifice for connection to the open air (34) and, onthe other hand, its lower part is disengaged from the orifice forevacuation of the liquid (36) allowing the liquid to be evacuated underthe influence of gravity.
 2. Device as described in claim 1,characterised by the fact that the orifice for connection to the openair (34) is defined by a substantially cylindrical sealing surface(34B), and the upper part (42) of the obturator (40) includes an O-ringseal (44) co-operating with the said sealing surface (34B) when theobturator (40) is in the sealing position.
 3. Device as described in oneof claims 1 or 2, characterised by the fact that the orifice forevacuation of the liquid (36) is defined by a substantially cylindricalsealing surface (36A), and the lower part (48) of the obturator (40)includes an O-ring seal (50) co-operating with the said sealing surface(36A) when the obturator (40) is in the sealing position.
 4. Device asdescribed in claims 2 and 3 taken together, characterised by the factthat the sealing surface (34B) of the orifice for entry of air (34) ismore extended longitudinally than that (36A) of the orifice forevacuation of the liquid (36).
 5. Device as described in any one of thepreceding claims, characterised by the fact that the orifice forconnection to the open air (36) is threaded, and the upper part (42) ofthe obturator (40) is threaded to co-operate with the orifice forconnection with the open air when the obturator (40) is in the sealingposition.
 6. Device as described in claim 5, characterised by the factthat the obturator (40) includes, at one of its end, a head (46) forscrewing-unscrewing the rod.
 7. Device as described in claim 6,characterised by the fact that the obturator (40) includes, at its endopposite that including the said head (46), a substantially flat surface(52) for abutment against a complementary surface (54) of the casing(10; 141).
 8. Device as described in any one of the preceding claims,characterised by the fact that the obturator is in the form of a rod(40) including a standard part (56) for taking up play in thepositioning or the orifices for entry of air (34) and evacuation of theliquid (36).
 9. Device as described in claim 8, characterised by thefact that the said standard part (56) is formed of a flexible material.10. Device as described in one of claims 8 or 9, characterised by thefact that the said standard part (56) is of flexible structure. 11.Device as described in any one of the preceding claims, characterised bythe fact that the means for evacuation of the liquid include an outflowpipe (32) for the liquid connected to the orifice (36) for evacuation ofthe liquid (36) and rigidly attached to the casing (10; 140).
 12. Deviceas described in any one of the preceding claims, characterised by thefact that the filtration unit (7; 114) includes means (12) for filteringgas-oil, the residual liquid being water.
 13. Device as described inclaim 12, characterised by the fact that it includes an electricalheating unit (110) which comprises a casing (120) internally defining achamber for heating the gas-oil to be filtered, and means (126, 144) fordirect and tight connection of the chambers of the heating (110) andfiltration (114) units, and by the fact that it includes means forassembly of the casings (120, 140) of the said units (110, 114). 14.Device as described in claim 13, characterised by the fact that theconnection means include a sleeve (126) rigidly attached to the casing(120) of one (110) of the heating and filtration units, and an orifice(144) for reception of the said sleeve (126) formed in the wall of thecasing (140) of the other (114) of the said units.
 15. Device asdescribed in claim 14, characterised by the fact that the sleeve (126)and the casing (120) to which it is rigidly attached form a singlepiece.
 16. Device as described in any one of claims 14 or 15,characterised by the fact that the connection means (126, 144) areprovided with sealing means (127).
 17. Device as described in one ofclaims 13 to 16, characterised by the fact that the assembly meansinclude means for detachably fixing the casing (120) of one (110) of theheating and filtration units to the casing (140) of the other (114) ofthe said units, the casings of the said units co-operating bycomplementarity of shape.
 18. Device as described in claim 17,characterised by the fact that the fixing means include a slidingconnection with a slideway (130, 150) between the heating unit (110) andthe filtration unit (114), and means (128, 148) for retaining one of thesaid units (110, 114) in translation relative to the other.
 19. Deviceas described in claim 18, characterised by the fact that the connectionwith a slideway (130, 150) provides an inclined ramp (130) for slidingof one of the said units (110, 114) on the other.
 20. Device asdescribed in claims 18 or 19, characterised by the fact that the meansfor retention in translation include a wedge (128) rigidly attached tothe casing (120) of one of the said units, and a tab (148) rigidlyattached to the casing (140) of the other of the said units, arrangedtransversally to the direction of translation and suitable to retain thewedge (128) in translation when the casings (120, 140) of the said unitsare fixed one to the other.
 21. Device as described in claim 20,characterised by the fact that on the face (128B) of the wedge (128)bearing on the tab (148) when the casings (120, 140) of the said unitsare fixed one to the other, is arranged at least one retaining notch.22. Device as described in claims 20 or 21, characterised by the factthat the wedge (128) includes an inclined face (128A) for pushing backthe tab (148) at the movement of fixing of the heating unit (110) on thefiltration unit (114).
 23. Device as described in any one of claims 20to 22, characterised by the fact that the tab (148) includes a sectilepart (148A).
 24. Device as described in claim 23, characterised by thefact that the heating unit (110) has a longer life than that of thefiltration unit (114), a same heating unit being suitable for successiveconnection in time to a plurality of filtration units.
 25. Device asdescribed in any one of claims 17 to 24, characterised by the fact thatthe fixing means include means (128C, 162) for retention in a directiontransversal to the direction of translation of one of the said units(110, 114) relative to the other.
 26. Device as described in claim 25,characterised by the fact that the transversal retention means includetwo ramps (128C, 162) for transversally offsetting one of the said units(110, 114) relative to the other, the respective directions oftransversal offset of the said two ramps being opposite.
 27. Gas-oilsupply line, in particular for a diesel engine, of the low pressure typeand including a tank (4), a filtration device (6, 106) and a gas-oilpump (8), characterised by the fact that the filtration device (6, 106)is constructed in accordance with any one of claims 1 to 26.